[gcc r13-4392] libstdc++: Remove unnecessary tag dispatching in std::vector

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:81cf0354d5f81f2c7600a3bc7ae4600757286995

commit r13-4392-g81cf0354d5f81f2c7600a3bc7ae4600757286995
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Nov 29 15:19:33 2022 +0000

    libstdc++: Remove unnecessary tag dispatching in std::vector
    
    There's no need to call a _M_xxx_dispatch function with a
    statically-known __false_type tag, we can just directly call the
    function that should be dispatched to. This will compile a tiny bit
    faster and save a function call with optimization or inlining turned
    off.
    
    Also add the always_inline attribute to the __iterator_category helper
    used for dispatching on the iterator category.
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/stl_iterator_base_types.h (__iterator_category):
            Add always_inline attribute.
            * include/bits/stl_vector.h (assign(Iter, Iter)): Call
            _M_assign_aux directly, instead of _M_assign_dispatch.
            (insert(const_iterator, Iter, Iter)): Call _M_range_insert
            directly instead of _M_insert_dispatch.

Diff:
---
 libstdc++-v3/include/bits/stl_iterator_base_types.h | 1 +
 libstdc++-v3/include/bits/stl_vector.h              | 6 +++---
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/libstdc++-v3/include/bits/stl_iterator_base_types.h b/libstdc++-v3/include/bits/stl_iterator_base_types.h
index 9eecd1dd855..5d90c0d8ea7 100644
--- a/libstdc++-v3/include/bits/stl_iterator_base_types.h
+++ b/libstdc++-v3/include/bits/stl_iterator_base_types.h
@@ -233,6 +233,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  sugar for internal library use only.
   */
   template<typename _Iter>
+    __attribute__((__always_inline__))
     inline _GLIBCXX_CONSTEXPR
     typename iterator_traits<_Iter>::iterator_category
     __iterator_category(const _Iter&)
diff --git a/libstdc++-v3/include/bits/stl_vector.h b/libstdc++-v3/include/bits/stl_vector.h
index b4ff3989a5d..e87fab0e51c 100644
--- a/libstdc++-v3/include/bits/stl_vector.h
+++ b/libstdc++-v3/include/bits/stl_vector.h
@@ -821,7 +821,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	_GLIBCXX20_CONSTEXPR
 	void
 	assign(_InputIterator __first, _InputIterator __last)
-	{ _M_assign_dispatch(__first, __last, __false_type()); }
+	{ _M_assign_aux(__first, __last, std::__iterator_category(__first)); }
 #else
       template<typename _InputIterator>
 	void
@@ -1478,8 +1478,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	       _InputIterator __last)
 	{
 	  difference_type __offset = __position - cbegin();
-	  _M_insert_dispatch(begin() + __offset,
-			     __first, __last, __false_type());
+	  _M_range_insert(begin() + __offset, __first, __last,
+			  std::__iterator_category(__first));
 	  return begin() + __offset;
 	}
 #else